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As a prominent member of freshwater and coastal fish faunas, Coilia nasus migrates annually from the sea up the Yangtze River in China to spawn. It is traditionally believed that C. nasus generally do not feed during their spawning migration. However, we recently documented the occurrence of food intake phenomenon in C. nasus following voluntary fasting. The purpose of the current study is to explore the metabolic mechanisms on C. nasus in response to food intake during migration. A total of 23,159 differentially expressed mRNA molecules and 204 metabolites were identified in transcriptome and metabolome analyses. Our results provide insights into the activation of energy consumption and reinforcement of energy storage during migration, and also identify key genes involved in food intake regulation. Our findings will be useful for future research on population recruitment and energy utilization in wild C. nasus. • Metabolic changes in feeding C. nasus were quantified for the first time. • Energy consumption was activated by feeding. • Energy storage was reinforced by feeding. • Metabolic mechanisms lay a foundation for the study of migratory ecology in C. nasus. [ABSTRACT FROM AUTHOR]

Coilia nasus is a valuable commercial migratory fish species with ecological and economic importance in China. To explore the molecular mechanisms underlying the response to food intake, the stomach transcriptomes of feeding and non‐feeding C. nasus were analysed via RNA‐seq. A total of 610,640,864 clean reads were obtained, and annotation to six databases identified 63,567 unigenes. Comparative analysis of the gene expression in feeding and non‐feeding C. nasus identified 1,968 differentially expressed genes (p <.05), including 1,180 up‐regulated and 788 down‐regulated genes. Our results showed that stomach distention activated the vagal afferent neurons, resulting in satiation. Several of the most relevant appetite genes (e.g. leptin receptor [LepR], somatostatin [SS], nucleobindin‐2 [NUCB2], 5‐hydroxytryptamine receptor [5‐HTR], growth hormone receptor [GHR]) were also involved in the regulation of food intake and led to the termination of feeding. Furthermore, significant differences were observed in the genes encoding key enzymes involved in metabolism such as the tricarboxylic acid cycle (TCA) pathways, fatty acid synthesis and glycolysis, indicating that C. nasus utilizes food for its energy and nutrient contents to support life and gonadal development. These findings provide valuable insights into the mechanisms underlying appetite and metabolic regulation in anadromous fish and create a foundation for further research on C. nasus artificial breeding and migration energetics. [ABSTRACT FROM AUTHOR]